For example, a conventional LVDS (LVDS: Low Voltage Differential Signaling) transmitter is composed of two current sources, an op amp (OPAMP), P-channel (PCH) switch/N-channel (NCH) switch for controlling the flow direction of the drive current, and a timing controller for controlling said switches. The current sources provide drive currents, and the op amp controls the common mode voltage of the transmitter output. Said PCH/NCH switches control the flow direction of the drive current. When the drive current is switched, the timing controller changes the switching timing for each switching cycle in order to prevent large changes in the drive current. The rise time and fall time are determined to a certain extent by the interval in which the timing is changed. However, because the conventional timing controller made up of a conventional inverter chain (having plural inverters connected in series), variations in the power source, the manufacturing process and temperature lead to an increase in the variation of the switching timing of the timing control signal. As a result, variations in the rise time and fall time in the transmitter output increase.
In the prior art, in order to realize a lower power consumption corresponding to the inherent characteristics of an LSI, and for other purposes, there is a technology that adopts an autonomous function of the LSI chip, see “Non-Patent Reference 1 Autonomous LSI, seeking homogeneity,” Nikkei Electronics, Mar. 29, 2004, pp. 109-129.
More specifically, in the power control technology for reducing power consumption used in a portable information terminal controller, in order to realize lower power consumption, a “delay synthesizer circuit” is used (see p. 123, FIG. 3). This delay synthesizer circuit approximately reproduces the delay time of the critical bus. The virtually reproduced delay time is compared with a target value. If the delay time is less than the target value, the power source voltage supplied to the LSI chip is further reduced. As a result, the lowest necessary power source voltage is supplied to LSI.
In the power control technology for lower power consumption using said delay synthesizer circuit, it is necessary to use circuits for delay time generation, measurement and comparison, so that the circuit scale required for realizing lower power consumption is increased.
A general object of the present invention is to provide a circuit characteristics controller that can control the characteristics of the circuit on the basis of the characteristics of the transistors without using a large scale circuit. Another object of the present invention is to provide a circuit device using said circuit characteristics controller.